1. Field of the Invention
This invention relates to waste water treatment systems and, more particularly, to structure for skimming surface scum off water in a filter compartment.
2. Background Art
"Moving bridge filters" have long been used with a high degree of success in treating waste water. This type of filter typically utilizes sand as a filtering media and is provided with a media bed which is divided into a number of compartments or cells. Each of the cells, in turn, is provided with a port from which purified water may flow to a point of disposition after water to be purified has been introduced into the filter above the cells.
As is well known, during the course of use of such filters, the upper surface of the filter media progressively becomes clogged by material filtered from the influent water and periodically such material must be removed to maintain the filtering efficiency of the system. In a typical moving bridge filter, a hood-like structure, typically termed a waste water manifold is suspended from a moving bridge and may be moved over the bed of filtering material to be aligned over any one of the cells. A backwash manifold assembly is moved in unison therewith to align with the individual port for the corresponding cell. Backwash water is then introduced into such port to pass upwardly through the filter media in the corresponding cell. As the backwash water passes through the filter media in each cell, it loosens and carries with it clogging material which is collected by the waste water pump and manifold. Some of the dislodged material may escape the waste water manifold and will float to the surface of the water to accumulate as a scum layer, which must be periodically skimmed and disposed of.